1. Field of the Invention
The present invention pertains to methods and apparatus for separating vapors from gas mixtures. Specifically, it pertains to methods and apparatus for separating vapors from gas mixtures by condensation.
2. Brief Description of the Prior Art
Vapors are conventionally separated from gas mixtures by condensation, absorption and adsorption. Vapor separation by condensation requires low temperatures for efficient operation. Conventional condensation separators use externally powered refrigeration systems to achieve the requisite low temperatures. Even utilizing heat exchangers for efficient heat recovery, the energy cost of such a system is high.
Another type of conventional vapor separator uses the Joule-Thomson effect produced by expansion of gas mixtures from high pressure through throttling valves (commonly called expansion valves) to reach temperatures low enough for condensation. The Joule-Thomson effect requires very high pressures for most substances and does not produce large decreases in temperature so that extensive precooling is necessary. This requires recovery heat exchangers or external refrigeration.
Another type of conventional vapor separator utilizes isentropic expansion in a turbine or other mechanical device to extract mechanical energy of expansion in order to reach low temperatures. While isentropic expansion can produce very low temperatures with modest pressure decreases, the mechanical devices are complex and expensive, and are generally only feasible for large installations.
There are many variations of the above separating processes, as well as processes for separating liquids from other liquids and solid matter from liquids or gases. A few examples of such may be seen in U.S. Pat. Nos. 2,676,667; 2,816,490; 3,546,891; 3,710,554; and 3,972,698.